This invention relates to a process for the production of superconducting films.
In recent years, intensive and extensive studies have been made of methods for producing high-temperature superconducting films.
Superconducting films are generally prepared by depositing a specific metal oxide on a substrate by means of the magnetron sputtering method, laser sputtering method, CVD (Chemical Vapor Deposition) method, MBE (Molecular Beam Epitaxy) method, and so on. In these methods, superconducting films having high Tc (critical temperature) have often been prepared successfully by carrying out high-temperature annealing after film deposition so as to adjust the oxygen concentration in the film. It is known, however, that the post-annealing is likely to cause various problems due to the high substrate temperature such as diffusion of substrate elements into films. This limits the practical utility of the resulting films, especially in their electronic device applications.
It has been proposed, on the other hand, to carry out the film deposition process in the presence of oxygen thereby effecting the adjustment of oxygen concentration during the formation of films without the need for post-annealing. This method enables the production of superconducting thin films at a substrate temperature which is to some extent lower than that required for the post-annealing. This method, however, still requires a considerably high substrate temperature in the order of 600.degree.-900.degree. C., and thus is still inadequate for applications in electronic devices. Accordingly, there has been a strong desire in the art to establish a technique which can substantially lower a substrate temperature in the film deposition process.